Physical Oceanography Lunch Seminar 1/24/2024

Wednesday, January 24, 12:30 PM to 01:30 PM PST

Physical Oceanography Lunch Seminar 

MSB 123

Speaker: Melissa Moulton, UW APL & NCAR

Title: Modeled Coastal-Ocean Pathways of River-Sourced Contaminants in the Aftermath of Hurricane Florence

Abstract: Heavy rainfall associated with tropical storms causes flooding of wastewater facilities, industrial waste storage sites, and agricultural land including concentrated animal feeding operations. The resulting release of contaminants, nutrients, and debris to the coastal ocean causes water quality impacts including algae blooms, fish kills, and exposure of people to contaminated flood waters and seafood. In the weeks following Hurricane Florence, which made landfall in North Carolina in September, 2018, extreme flooding and river discharge resulting from historic rainfall carried pollutants, sediment, organic matter, and debris to the coastal ocean. Here, the ocean pathways of these land-sourced contaminants are investigated using passive tracers in the Regional Ocean Modeling System (ROMS) within the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) modeling system, with a river point source from a hydrologic model simulation (WRF-Hydro) of the Cape Fear River Basin. Following Hurricane Florence, there was westward transport of contaminants, along with intermittent storage and release of material near the river mouth, modulated by alternating upwelling and downwelling winds. This led to a delayed onset and long duration of contaminants affecting beaches 100 km west of the river mouth, days to weeks after the storm. For simulations of synthetic events with 200%, 50%, or 25% of the Hurricane Florence discharge, there is more rapid westward propagation of contaminants for larger discharge. Simulations with fixed post-storm wind direction have a bidirectional pattern for upwelling winds, and an enhanced westward coastal current for downwelling winds. Maps of the onset and duration of hypothetical water quality hazards for a range of weather conditions are presented to provide guidance to managers deciding when to perform water quality sampling and issue swimming or shellfishing advisories.